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AAO Press Releases

Tuesday, 14 July 1998

The Fate of Our Sun?

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Astronomers at the Anglo-Australian Observatory (AAO) are making great strides toward a better understanding of how stars like our sun will eventually die. Over the next few years they expect to increase the number of known stars caught gracefully ejecting their outer envelopes of gas --an event that signals their death-by more than half.

Dr Quentin Parker of the AAO announced this result at the recent meeting of the Astronomical Society of Australia in Adelaide.

The objects are called planetary nebulae, and over just a few nights observing recently, AAO astronomers confirmed the discovery of almost 100 previously unknown stellar corpses.

Planetary nebulae have nothing to do with planets but were so named by William Herschel in 1785 because of the their resemblance to the disc shape of very faint planets.

Dr Parker leads the team of astronomers that made the discoveries. "At this rate we can expect about 1000 new planetary nebulae to be confirmed in the southern Milky Way Galaxy over the next three years," he said.

"It has taken more than 200 years to uncover the 1500 currently known planetary nebulae in the entire Milky Way Galaxy. Since this is a survey of the south only, our new sample is even more significant," Dr Parker added.

This is the first important discovery from the Hydrogen-alpha survey of the southern Milky Way begun in July 1997. The three-year survey uses an H-alpha interference filter of exceptional quality on the Anglo-Australian Observatory's UK Schmidt Telescope near Coonabarabran in New South Wales.

"These new planetary nebulae are resolved, extended nebulae with low surface brightness, and up until now have been invisible, or barely detectable," Dr Parker said. "Previously 60% of known planetary nebulae have been point sources," he added.

It has only been possible to detect them with the specially designed narrow-band filter for the UK Schmidt Telescope. Dr Parker, who designed the filter said, "At 14 x 14 inches, it is one of the largest optical interference filters ever made for astronomy." The large size of the filter and the wide field of the UK Schmidt Telescope enable astronomers to scan huge areas of the heavens for these planetary nebulae.

The sheer numbers of new planetary nebulae being found by Dr.Parker and colleague Mr.Malcolm Hartley has excited astronomers who will use the discoveries to study stellar and galactic evolution. The varied and interesting planetary nebulae shapes may also tell us something about the interstellar medium and the possible presence of binary companions or even possible associated sub-solar 'planets.'

The attached picture of one of the new planetary nebulae was made from three separate exposures using the Taurus Tunable Filter on the Anglo-Australian Telescope.

Further details about the survey and discoveries can be found on the web.

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Roger Bell
14 Jul 1998